In Long Term Evolution (LTE) Release 12 in 3rd Generation Partnership Project (3GPP), “local area enhancement” or “small cell enhancement” has become one of subjects for discussion for accommodation of local huge traffic, improvement of throughput, efficient utilization of a high frequency band, and the like (refer to Non-patent Literature 1). In the local area enhancement or the small cell enhancement, a low-power node (LPN) that forms a small cell is used.
Furthermore, a C/U plane split scenario has been proposed regarding the small cell enhancement. In C/U-plane split, a macro cell provides a control plane (e.g., a Radio Resource Control (RRC) connection and a Non-Access Stratum (NAS) message transfer) to a mobile station (User Equipment (UE)), and the small cell provides a user plane to the UE. When looking at a specific introduction example regarding a Control plane (C-plane), the macro cell can maintain a good connection with the UE by a wide coverage using a low frequency band, and can support mobility of the UE. Meanwhile, when looking at the user plane (U-plane), the small cell can provide local high throughput to the UE by using a wide bandwidth in a high frequency band.
In the C/U plane split scenario, a case is also assumed where the small cell need not transmit existing cell-specific signals/channels, for example, a PSS (Primary Synchronization Signal), a Secondary Synchronization Signal (SSS), a Cell-specific Reference Signal (CRS), a Master Information Block (MIB), and a System Information Block (SIB). Accordingly, such new small cell may be called a phantom cell. In addition, a base station (eNB) or an LPN that provides such small cell may also be called a Phantom eNodeB (PhNB).